Remote center positioner

ABSTRACT

The invention is directed to a remote center positioner used to support an instrument and provide a center of spherical rotation, remote from any bearings or mechanical supports, at a desired location of the instrument. The remote center positioner is particularly useful in laparoscopic surgery to constrain a surgical instrument to move around a fixed center of rotation remote from any bearings or mechanical supports and coincident with an entry incision in the abdominal wall.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/133,206, filed on Apr. 26, 2002, now U.S. Pat. No. 6,758,843, whichis a continuation of U.S. application Ser. No. 09/568,089, filed May 9,2000, now U.S. Pat. No. 6,406,472, which is a continuation of U.S.application Ser. No. 09/149,828, filed Sep. 8, 1998, now U.S. Pat. No.6,106,511, which is a continuation of U.S. application Ser. No.08/504,620, filed Jul. 20, 1995, now U.S. Pat. No. 5,817,084, which is acontinuation of U.S. application Ser. No. 08/298,550, filed Aug. 30,1994, now abandoned, which is a divisional of U.S. application Ser. No.08/062,404, filed May 14, 1993, now abandoned, the full disclosures ofwhich are incorporated herein by reference.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH OR DEVELOPMENT

This invention was made with Government support under contract awardedby the National Institute for Health (NIH) under grant number5R01GM-44902-02. The Government has certain rights in this invention.

BACKGROUND OF THE INVENTION

The present invention is directed to a remote center positioner used tosupport an instrument and provide a center of spherical rotation, remotefrom any bearings or mechanical supports, at a desired location of theinstrument. Specifically, the remote center positioner is useful inlaparoscopic surgery to constrain a surgical instrument to move around afixed center of rotation remote from any bearings or mechanical supportsand coincident with an entry incision in the patient's abdominal wall.

In standard laparoscopic abdominal surgery, the patient's abdomen isinsufflated with gas, and cannulas are passed through small(approximately ½ inch) incisions to provide entry ports for laparoscopicsurgical instruments. The laparoscopic surgical instruments generallyinclude an laparoscope for viewing the surgical field, and working toolssuch as clamps, graspers, scissors, staplers, and needle holders. Theworking tools are similar to those used in conventional (open) surgery,except that the working end of each-tool is separated from its handle byan approximately 12-inch long extension tube. To perform surgicalprocedures the surgeon passes instruments through the cannulas andmanipulates them inside the abdomen by sliding them in and out throughthe cannulas, rotating them in the cannulas, and “levering” (pivoting)them around centers of rotation approximately defined by the incisionsin the muscles of the abdominal wall. The abdominal incisions do notprovide stable reference positions or points of rotation, and so inorder to maintain accurate positional control of an instrument duringmanipulation, the surgeon may need to manually constrain it to pivotaround a fixed point coincident with the incision. Manual support of thepivot point is particularly important when the surgeon manipulateslaparoscopes or other heavy instruments. Mechanical clamping devices'are used to support the instruments in fixed orientations, but thesedevices do not provide a remote center of rotation for positioning theinstruments.

In robotically assisted and telerobotic laparoscopic abdominal surgerythe position of the surgical instruments is controlled by servo motorsrather than directly by hand or with fixed clamps. With servo control, ameans must be provided to ensure that the surgical instrument isconstrained to move around a fixed center of rotation coincident with anentry incision in the patient's abdominal wall. Any other types ofmotion such as translation or rotation about other centers could causepatient injury.

Heretofore, there have been mechanisms directed to providing assistancein surgery. Thus, U.S. Pat. No. 4,756,655 to Jameson is directed to amanipulating mechanism having a control handle adapted to be positionedfreely in three dimensions, a fixture for supporting a tool to bepositioned, a linkage system which causes the end of the tool to move inthe same direction as the control handle and a support structure. Thelinkage system includes a first linkage connected between the controlhandle and an effective ball-and-socket joint and a second linkageconnected between the effective ball and socket joint and the fixture.Each linkage includes four link members rotatably connected in aparallelogram and a gimbal connected to one of the link members formounting the linkage from the support structure.

The linkage system includes a first linkage connected between thecontrol handle and a joint and a second linkage connected between thefirst linkage and the fixture. In the preferred embodiments, the linkagesystem is comprised of two motion translation mechanisms connected inseries through an effective ball-and-socket joint, where eachtranslation mechanism is essentially a pantograph adapted for rotationwith respect to the support structure about two perpendicular axes. Themotion of the control handle induces oppositely (or similarly, dependingon the embodiment) directed motion of the ball-and-socket point by meansof one translation mechanism which in turn causes similarly directedmotion of the tool by means of the second translation mechanism so thatthe motion of the tool is in the same direction as the motion of thecontrol handle. The linkage system is directed to a master reflectionsystem controlling a slave reflection mechanism and does not provide aremote center of spherical rotation.

U.S. Pat. No. 4,143,652 to Meier and Dbaly discloses a surgicalretaining device for holding a surgical instrument in place, typicallywith hooks. The device includes a holder block for displaceably securingthe surgical retaining device at a stationary object and at least oneinsert element into which there can be inserted and fixedly clamped thesurgical instrument. Between the insert element and the holder blockthere is arranged a double-arm pivotable stand possessing anintermediate pin joint. The pivotable stand is connected at one end bymeans of a ball-and-socket joint at the insert element and at its otherend by means of a further ball-and-socket joint with an overhang armwhich can be fixedly clamped at random elevational and angular positionswith respect to the holder block at the latter.

A paper given at the IEEE Engineering in Medicine and Biology Society11th Annual International Conference in 1989 entitled SMOS:Stereotaxical Microtelemanipulator for Ocular Surgery shows a structurefor use in ocular vitrectomy, and other medical fields such as radialkeratotomy and plastic surgery. FIGS. 2 and 3 of the paper shows themechanical structure of the SMOS. A carrier holds a rotatably mountedcurved wrist. An instrument holder is movably mounted to the wrist forcarrying an instrument or needle for working in the eye keeping theneedle centered on the entrance aperture. This is described as realizedin spherical coordinates in a reference whose zero point is the entranceaperture A. The mechanism creating these movements, which are inthemselves the main actions of the vitrectomy operation, is called thewrist of the microtelemanipulator.

An article entitled “Robotic Surgery” in the March 1993 issue of IEEEEngineering in Medicine and Biology shows a motorized frame (FIG. 8) foruse in prostate surgery. FIG. 8 shows a schematic layout of the mainmechanical components of the device called SARP. The working envelope issmall and can be flexibly constrained using mechanical stops to improvesafety. The envelope is approximately the frustum of a cone. Severalcones may be needed, depending on the size of the prostate, to removethe unwanted enlarged tissue from within the prostate.

The manual frame can only produce conical cavities because it ismanually driven. However, the motorized frame is capable of producingboth conical and barrel shape cavities. As a start, conical cavities areadvocated to avoid moving along more than one axis at a time. Conicalcavities are easy to produce using hot loop electrosurgery. Similar tothe manual frame, a ring shape frame fitted with a diametrical arch is acarriage that carries the resectoscope. A C-shaped bracket fixed to theresectoscope helps ease the introduction of the motorized frame to theresectoscope. The axes are designed to be driven by motors. Back drivingis possible when the servo action is disabled. Successive cuts are madeby extending and retracting the cutting loop repeatedly and turning onthe cutting current at the return stroke of the cutter. The ring movesto a new position for each cut. Several conical cavities can be resectedfrom the prostate to relieve blockage. To achieve one or more of theseconical cavities inside the prostate, the frame is fixed to a headtravel so that it can move axially along the rotation axis of the ringaxis.

None of the above-mentioned devices provide a light weight simpleapparatus for providing a remote center of rotation for use in surgerywith minimal obstruction of the surgical field as is disclosed andclaimed herein.

BRIEF SUMMARY OF THE INVENTION

In a broad aspect an apparatus is provided for moving an instrumentabout a spherical center of rotation at a desired location of theinstrument. A base support means is adapted to be fixedly mounted to asurface. First linkage means are pivotally mounted on the base supportmeans for rotation about an axis. Holding means are provided for holdingan instrument in a position so that the desired remote center ofspherical rotation of the instrument lies on the axis of rotation of thefirst linkage means. A second linkage means is connected to the holdingmeans and pivotally connected to the first linkage means so that theremote center of spherical rotation of the instrument is maintained atthe desired location.

The present invention provides a device for providing a remote center ofspherical rotation for an instrument. A pivot joint having an x-x axisof rotation has a first linkage having one end pivotally mountedthereon. The axis of rotation of the first linkage is normal to andintersects the x-x axis. The other end is remote from the pivot joint. Aparallelogram linkage is provided with a driving end and a remote end.The parallelogram linkage includes two sets of two corresponding memberspivotally connected in a parallelogram. The parallelogram linkage islocated in a plane parallel with the first linkage and has the drivingend pivotally connected to the remote end of the first linkage. Amounting means for an instrument extends from the remote end of theparallelogram linkage. The mounting means is adapted to position theaxis of the instrument held thereby to intersect the x-x axis to providea center of spherical rotation for the instrument at a desired location.

In a more specific aspect the invention provides a device for providinga remote center of spherical rotation for an instrument for conductinglaparoscopic surgery including a base support means adapted to befixedly mounted to a surface and a pivot plate pivotally mounted to thebase support means and having a rotational axis thereabout. At least apair of linkage elements are extended from the pivot plate in parallelplane relationship. One end of the linkage elements is pivotally mountedin spaced apart relationship to the pivot plate. A parallelogram linkagemeans is connected to the linkage elements and includes two sets of twocorresponding link members pivotally connected in a parallelogram, oneof the sets of two sets of the two corresponding link members adapted toremain always parallel to the rotational axis, one of the link membersof the set of corresponding link members adopted to remain alwaysparallel to the rotational axis being pivotally connected to bothlinkage elements, one of the linkage elements being pivotally connectedto both link members adopted to remain always parallel to the rotationalaxis. The parallelogram linkage means has an operating end and a drivingend. An instrument element extends from the operating end of theparallelogram linkage means for movement therewith. The instrumentelement intersects the rotational axis at the location on the elementdesired for the remote center of rotation.

The remote center positioner is useful in a variety of applications. Forexample, supporting a microscope or other instrument to scan over andinspect a spherical surface. Various tools or instruments (manually orrobotically positioned) that are passed through narrow entry ports canbe supported by the apparatus of the present invention. Other usesinclude robotically-assisted positioning of an laparoscope forlaparoscopic surgery, with the user commanding the position andorientation of the laparoscope via digital speech recognition,foot-switches, head-tracking or eye-tracking devices; support ofmanually-positioned laparoscopes or other surgical instruments duringlaparoscopic surgery; and telerobotic manipulation of laparoscopicsurgical instruments (laparoscopes and various working tools) in whichthe positions of the working end of the tools are under servo control,and follow the motions of a surgeon's hands as he manipulates inputcontrol devices at a location that may be remote from the patient.Position, force, and tactile feedback sensors may be employed totransmit position, force, and tactile sensations from the working tooltips back to the surgeon's hands as he operates the telerobotic system.

OBJECT OF THE INVENTION

A particular object of the present invention is to provide apparatususeful to support an instrument or the like and includes the ability tomove the instrument to perform a variety of tasks while maintaining acenter of spherical rotation at a desired location of the instrument.Additional objects and advantages of the present invention will becomeapparent from the description of the various embodiments thereof read inlight of the attached drawings which are made part of thisspecification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a elevation view of an embodiment of a remote centerpositioner;

FIG. 2 is an elevation view of the preferred embodiment of a remotecenter positioner,

FIG. 2 a is an enlarged sectional view taken at section a—a of FIG. 2;

FIG. 3 is an end view of the preferred embodiment of the remote centerposition of FIG. 2;

FIG. 4 is a elevation view illustrating an embodiment of the remotecenter positioner in accordance with the invention having an adjustablecenter distance;

FIG. 5 is an elevation view illustrating a motor driven application ofthe remote center positioner in accordance with the present invention;

FIG. 6 is an elevation view illustrating a manual application of theremote center positioner in accordance with the present invention;

FIG. 7 is an elevation view of another embodiment of apparatus of theinvention;

FIG. 7 a is a sectional view taken at line a—a of FIG. 7;

FIG. 8 is an elevation view of another embodiment of apparatus or theinvention; and

FIG. 8 a is a sectional view taken at line a—a of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is an elevation view of an embodiment of a remote centerpositioner in a basic form in accordance with the present invention. Afirst linkage means is indicated generally by the numeral 21 and asecond linkage in the form of a parallelogram is indicated by thenumeral 23. The first linkage means is pivotally mounted on a base platefor rotation about an x-x axis. The second linkage means is pivotallyconnected to the first linkage means and is adapted to move in a planeparallel to the first linkage. Five link members (including extensionsthereof), 11, 12, 13, 14, and 15 are connected together with pivotjoints 16–20. A portion of element 13 extends beyond pivot 20 of theparallelogram linkage. The parallelogram linkage has an operating end atlink member 13 and a driving end at link member 12. The elongatedelement 13 may, as desired later, carry a surgical instrument or otherdevice. The pivot joints allow relative motion of the link members onlyin the plane containing them.

A parallelogram linkage is formed by corresponding link members 14, 15and link members 12 and 13. The portions of link members 14 and 15 ofthe parallelogram are of equal length as are the portions of members 12and 13 of the parallelogram. These members are connected together in aparallelogram for relative movement only in the plane formed by themembers. A rotatable joint generally indicated by the numeral 22 isconnected to a suitable base 24. The rotatable joint 22 is mounted on abase plate 26 adapted to be fixedly mounted to the base support means24. A pivot plate 28 is pivotally mounted to base plate 26 by suitablemeans at, such as, pivots 30, 32. Thus pivot plate 28 may be rotatedabout axis x-x through a desired angle θ2. This may be accomplishedmanually or by a suitable pivot drive motor 34.

A first linkage is pivotally mounted on the pivot plate 23 of therotatable joint 22. The linkage elements 11, 12 and the link membersrelatively stiff or inflexible so that they may adequately support aninstrument used in surgical operations. Rods made of aluminum or othermetal are useful as such links. The linkage elements 11 and 12 arepivotally mounted on base plate 28 for rotation with respect to therotatable joint by pivots 36 and 38. At least one of the pivots 36, 38is positioned so that its axis of rotation is normal to and intersectsthe x-x axis. Movement may occur manually or may occur using a linkagedrive motor 40. The first linkage is also shaped in the form of aparallelogram formed by linkage elements 11, and 12; the portion of linkmember 15 connected thereto by pivots 16, 18; and base plate 28. One ofthe link members 15 is thus utilized in both the first 21 and second 23linkage means. Linkage element 12 also forms a common link of both thefirst linkage means 21 and the second linkage means 23. In accordancewith the invention, a remote center of spherical rotation 8 is providedby the above described embodiment of apparatus when the linkage element11 is rotated and/or when pivot plate 28 is rotated about axis x-x. Thusthe end of element 13 can be moved through desired angles θ1 and θ2 orrotated about its own axis while the remote center of rotation remainsat the same location.

The preferred embodiment of apparatus assembled in accordance with thepresent invention is illustrated in FIGS. 2, 2 a and 3. FIG. 2 is anelevation view, FIG. 2 a is an enlarged sectional view taken at a—a ofFIG. 2 and FIG. 3 is an end view of the remote positioning apparatus.Many of the elements of the preferred embodiment are the equivalent toelements of the FIG. 1 embodiment. These elements will be designatedwith the same numbers primed in FIGS. 2 and 3. Thus a pivot plate 28′ isrotatably mounted on a base support means 26′ by suitable means such aspivots 30′, 32′. The pivot plate and the base plate form a rotatablejoint 22′ which has a rotation axis designated as x-x. The base platemay be fixedly mounted to a suitable base support means 24′.

Two linkage elements 11′ and 12′ extend from the pivot plate 28′.Mounting means 36′ and 38′ are provided to pivotally mount one end ofeach of the linkage elements to the pivot plate. The axis of rotation ofthe linkage elements are normal to and intersecting the x-x axis. Achannel shaped link member 115 is pivotally connected by suitable pivotjoints 16′ and 18′ to the other ends of linkage elements 11′, 12′(respectively) equidistant from pivot plate 28′. A corresponding linkmember 15′ is located internally of link member 115 and is pivotallyconnected to the upper end of linkage element 12′. A link member 13′corresponding in length to the link member 12′ between pivots 17′, 18′is pivotally connected to link member 15′ at pivot 19′ and to linkmember 115 at pivot 20′. An instrument mounting means 44 is fixedlymounted to link member 13′ for movement therewith. The axis of aninstrument held in the instrument mounting means 44 intersects the x-xaxis of the rotating joint 22′. Thus an instrument held in the mountingmeans would have a remote center of spherical rotation about theposition indicated by the numeral 8′ in FIG. 2.

A drive motor 434 incorporating a shaft-angle position sensor isoperably connected to the pivot plate 28′. A second drive motor 440incorporating a shaft-angle position sensor is operably connected tolinkage element 11′. Suitable motor drive and control circuits may beconnected to motor/sensor 440 and motor/sensor 434 via power and sensorcables 436 and 435 (respectively) to operate the present apparatus underopen-loop or closed-loop servo control. The details of the mountingarrangement for the instrument mounting means are shown in FIG. 2 awhich is a sectional view taken at a—a of FIG. 2. As there shown themounting means 44 is fixedly connected via multiple-axis force andtorque sensor 400 and pin member 118 to link member 13′ for movementtherewith. Link member 13′ is pivotally connected at pivot 20′ to thechannel shaped link member 115 by bearing means 116, 117 formed aboutpin member 118. Link member 15′ is pivotally connected to link member13′ at 19′ by means of bearing means 120 and pin member 121.

A suitable sensor interface circuit may be connected to the force andtorque sensor 400 via cable 401 so that sensor signals arising fromforces and torques applied to an instrument supported in the mountingmeans 44 can be detected and used for monitoring or controllingoperation of the present apparatus. For example, the sensor signals canbe used as feedback signals in master-slave force-reflecting teleroboticservo control of the invention such that the input control deviceresponds to forces exerted on the supported instrument and is notaffected by inertial loads, gravity forces, or external forces acting onlinkage elements other than mounting means 44.

An apparatus is provided for moving an instrument about a sphericalcenter of rotation at a desired location of the instrument. A basesupport means is adapted to be fixedly mounted to a surface. Firstlinkage means 11′, 12′ are pivotally mounted on the base plate forrotation about an axis. A holding means 44 is provided for holding aninstrument in a position so that the desired remote center of sphericalrotation of the instrument intersects the axis and a second linkagemeans 15′, 115 and 13′ is connected to the holding means and pivotallyconnected to the first linkage means by pivots 17′, 18′, 16′ whereby theremote center of spherical rotation of the instrument is maintained atthe desired location.

FIG. 4 is a schematic elevation view of another embodiment of apparatusassembled in accordance with the present invention. In many instances itmay be desirable to have a means of adjusting the remote center ofrotation 8′ relative to the mounted position of base plate 26′. Thus itwould be desirable to axially extend or retract the horizontal members14′, 15′ of the parallelogram linkage. The length of the twocorresponding members 14′, 15′ must be increased or decreased in equalamounts to maintain the parallelogram geometry of the linkage.

The axial length adjustment could be provided in many ways. For example,as shown in FIG. 4, a portion of members 14′, 15′ are provided withracks 42, 44. Tubular members 46, 48 enclose members 14′, 15′. Themembers 14′, 15′ are extended or retracted by suitable means such asdrive motor 50, motor lead 51 and drive belt 52. Other means for axiallyextending or retracting the members are available. For example, coupledlead screws could be used or the members could be manually fixed intothe desired position in the tubular members using ratchets, pins orspring detents.

FIG. 5 illustrates an embodiment of apparatus assembled in accordancewith the invention wherein a motor driven arrangement is positioned onthe operating end of the parallelogram linkage. A drive unit 60 isconnected by power and control cable 62 to a source of power and controland a cannula 64 is provided which may be passed through a patient'sabdominal wall. An instrument 66 is attached to an operating element 68and may be manipulated as indicated in FIG. 5. The remote centerpositioners as described heretofore will maintain the center ofspherical rotation at position 80 while the instrument 66 is beingmanipulated.

FIG. 6 is an elevation view illustrating a manual application of theremote center positioner of the present invention. A handle 71 foroperating a surgical instrument 73 is connected to the operating end ofthe remote center positioner. Movement of the cannula 75 will beconstrained to rotation about the center 80′ of spherical rotation.

FIG. 7 is an elevation view and FIG. 7 a is a sectional view taken ata—a of FIG. 7 of an embodiment of the invention which utilizes aflexible drive element in the linkage of the remote center positioner. Arotatable joint is indicated by the numeral 122. The rotatable jointrotates about an x-x axis. Thus pivot plate 128 can be rotated aboutpivots 130, 132 through a desired angle θ2 with respect to base plate126. A linkage element 111 is pivotally mounted on the pivot plate bypivot 133. The pivot 133 is positioned so that its axis of rotation isnormal to and intersects the x-x axis. A pulley 101 is positioned to becoaxial with the axis of rotation of the pivot 133. It is evident thatthe term pulley can include wheels, sprockets or the like. The pulley isfixedly connected to the base plate 128 by suitable means such as screws105, 107. Thus the pulley will not rotate with respect to the base plate128.

A link member 114 is pivotally connected by pivot joint 116 to linkageelement 111. A second pulley 121 coaxial with pivot 116 is fixedlyconnected to link member 114 by screws 146 and 147. A flexible drivelink 135 such as a belt, chain, or a cable is connected around thepulleys 121, 101 in a non slip mode such as a bicycle chain or timingbelt. Pulleys 121 and 131 are of equal diameter as are pulleys 142 and137. A link member 140 is pivotally connected to the operating end oflink member 114 by means of pivot joint 141.

A third pulley 137 coaxial with pivot 141 is fixedly connected to linkmember 140 by means of screws 143, 145. A fourth pulley 142 coaxial withpivot 116 is fixedly connected to link element 111 by screws 160 and16.1. A second flexible drive link 150 is connected around pulleys 137and 142 in non slip relationship. Thus when linkage element 111 isrotated about pivot 133 by linkage drive motor 149 for example, themotion is transmitted by the pulleys to link member 140 which isconstrained to move in parallel relationship with element 111. In thismanner a remote center of rotation is maintained as indicated by 180 inFIG. 7.

FIG. 8 is an elevation view and FIG. 8 a is a sectional view taken ata—a of FIG. 8 of another embodiment of the present invention.

A rotatable joint is shown and is indicated generally by the number 222.The rotatable joint rotates about a x-x axis. Thus pivot plate 228 canbe rotated around pivots 230, 232 through a desired angle θ2. A linkageelement 211 is pivotally mounted on the pivot plate 228 by pivot 233.The axis of the pivot 233 is located normal to and intersecting the x-xaxis of rotation. A pulley 201 is positioned to be coaxial with the axisof rotation of the pivot 233. The pulley is fixedly connected to thebase plate by suitable means such as screws 205, 207.

A pair of link members 214, 215 are pivotally connected to linkageelement 211 by pivots 212 and 216 respectively. The other end of thelink members 214 and 215 are pivotally connected to an instrumentholding means or the like indicated by 240 by suitable pivot joints 241,242. A second pulley 231 is fixedly connected to link element 215 bysuitable screws 251, 252. The pulley 231 is mounted coaxially with theaxis of rotation of the pivot joint 216. A flexible drive link 260 isconnected around both pulleys 201 and 231 in non slip relationship. Theeffect of this construction constrains link members 215 and 214 toremain parallel with the x-x axis during movement and also constrainselement 240 to remain parallel with linkage element 211 during movement,thus causing the center of spherical rotation of the instrument or thelike to remain at point 280.

The principles, preferred embodiments and modes of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments disclosed. Theembodiments are to be construed as illustrative rather than restrictive.Variations and changes may be made by others without departing from thespirit of the present invention. Accordingly, all such variations andchanges which fall within the spirit and scope of the present inventionas defined in the following claims are expressly intended to be embracedthereby.

1. A surgical manipulator for moving an instrument about a desiredspherical center of rotation at a desired location along the instrument,the manipulator comprising: a first linkage, including at least a firstrod, pivotally mounted for rotation about a first axis; an instrumentholder holding the instrument in a position so that the desired remotecenter of spherical rotation of the instrument intersects a second axisand the first axis; a second linkage, including at least a second rod,pivotally connected to the first linkage and the instrument holder suchthat the spherical center of rotation is maintained at the desiredlocation along the instrument; and wherein the first or second linkagesincludes a flexible drive element comprising a pulley and a flexibleelement connected around the pulley, the pulley rotationally affixed toone of the rods such that a movement of one of the linkages istransmitted to the other of the linkages by the flexible drive element.2. A surgical manipulator for moving an instrument about a desiredspherical center of rotation at a desired location along the instrument,the manipulator comprising: a base support adapted to be mounted to asurface; a first linkage pivotally mounted on the base support, thefirst linkage including a pulley rotationally fixedly mounted thereonadjacent to the base support; an instrument holder for holding theinstrument in a position with the desired remote center of sphericalrotation; a second linkage connected to the instrument holder andpivotally connected to the first linkage, the second linkage including apulley rotationally fixedly mounted thereon adjacent the pivotalconnection to the first linkage; and a flexible element connected aroundthe pulleys such that the remote center of spherical rotation of theinstrument is maintained at the desired location as the linkages aremoved.
 3. A surgical manipulator system comprising. a surgicalinstrument having an elongate shaft with proximal and distal ends, anend effector coupled to the distal end, and means for actuating the endeffector at the proximal end; a rotatable joint having an x—x axis ofrotation; a first linkage comprising one member having a first endpivotally mounted on the rotatable joint and a second end remote fromthe rotatable joint, the axis of rotation of the member of the firstlinkage being normal to and intersecting the x—x axis, the first linkagefurther comprising a first pulley rotationally fixedly mounted on therotatable joint in coaxial relationship with the axis of rotation of themember; a parallelogram linkage having a driving end and a remote end,the parallelogram linkage including two sets of two correspondingmembers pivotally connected in a parallelogram, the parallelogramlinkage being in a parallel-plane relationship with the first linkageand having the driving end pivotally connected to the remote end of thefirst linkage, a second pulley rotationally fixedly mounted to one ofthe two corresponding members at the driving end of the parallelogramlinkage coaxial with the pivotal connection between the driving end andthe remote end of the first linkage, the first and the second pulleyshaving the same diameter; a flexible element coupling the first pulleyto the second pulley; a drive for pivoting the end effector with respectto the instrument shaft; and a mount for the instrument extending fromthe remote end of the parallelogram linkage, the mount adapted toposition the instrument axis to intersect the x—x axis of the rotatablejoint at a location on the instrument desired for a remote center ofspherical rotation.
 4. A surgical manipulator for moving an instrumentabout a desired spherical center of rotation at a desired location alongthe instrument, the manipulator comprising: a first linkage, includingat least a first pivotally mounted rod; an instrument holder for holdingthe instrument; a second linkage including a second rod connected to theinstrument holder, the second linkage being pivotally connected to thefirst linkage so that the second rod such that the spherical center ofrotation is maintained at the desired location of the instrument;wherein the linkages include a channel-shaped element disposed aroundthe second rod, the second rod and the channel-shaped elementtransmitting the movement of the first rod to the instrument holder. 5.The surgical manipulator of claim 4, wherein the channel-shaped elementcomprises a substantially rigid sleeve disposed around the second rod,the second rod and the rigid sleeve transmitting the movement of thefirst rod to the instrument holder such that the instrument isconstrained to move in parallel relationship with the first rod.
 6. Asurgical manipulating system comprising: a surgical instrument having anelongate shaft with a proximal end and a distal end configured forintroduction into a patient; an instrument holder coupled to the shaftof the surgical instrument; a rotatable joint having an x—x axis ofrotation; a first linkage including one member having one end pivotallymounted on the rotatable joint and the other end remote from therotatable joint, an axis of rotation of the member intersecting the x—xaxis; a second linkage comprising a sleeve and a rod disposed within thesleeve, the rod and sleeve being connected to the instrument holder forconstraining the instrument holder to move such that the sphericalcenter of rotation is maintained at the desired location of theinstrument; wherein the instrument comprises an end effector coupled tothe distal end, means for actuating the end effector, and means forpivoting the end effector with respect to the instrument shaft.
 7. Aposition constraint apparatus for constraining the position of asurgical instrument during operation in a minimally invasive surgicalprocedure, the surgical instrument including at least an elongate shaft,the shaft having a distal working end, at least the distal working endof the shaft configured for insertion into a body cavity of a patient,the position constraint apparatus comprising: an articulate supportassembly having a plurality of linkages and joints wherein the pluralityof linkages and joints comprise at least one pulley and at least oneflexible element coupled to the pulley that is configured to constrainshaft motion relative to a center of rotation; an instrument engagingstructure coupled to the a distal portion of the articulate supportassembly; the instrument engaging structure arranged to engage thesurgical instrument so that the elongate shaft of the instrument ispermitted to move relative to the instrument engaging structure; thearticulate support assembly configured to constrain the position of theelongate shaft of the instrument relative to the center of rotation, sothat the shaft is maintained substantially aligned through the center ofrotation; and the position constraint apparatus configurable by anoperator so as to permit the center of rotation to be positioned at aselected point.